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From: chris@umcp-cs.UUCP
Newsgroups: net.unix-wizards
Subject: Re: _print/_doprnt
Message-ID: <7788@umcp-cs.UUCP>
Date: Sat, 7-Jul-84 21:12:42 EDT
Article-I.D.: umcp-cs.7788
Posted: Sat Jul  7 21:12:42 1984
Date-Received: Thu, 12-Jul-84 03:20:45 EDT
References: <1075@sri-arpa.UUCP> <2048@rlgvax.UUCP> <1472@pegasus.UUCP>
Organization: Univ. of Maryland, Computer Science Dept.
Lines: 55

As long as we're getting into *printf:

Here's a bunch of things I'd like to see in the stdio library:

a) sprintfl (or some similar name): like sprintf, but takes a maximum
   buffer length specification.  For example:

	char buf[N];
	.
	.
	.
	sprintfl(buf, N, "%s", foo);

   Avoiding overrun with plain ol' sprintf() is a pain.

b) v*printf versions of everything on Berkeley Unix(tm)

c) _IOSTRG flag working properly.  At least in BSD, _IOSTRG is
   *never* checked (not once!) so if you try to write sprintfl as

	/* sprintfl - vax version */
	char *
	sprintfl(buf, len, fmt, arg)
	register char *buf;
	register int len;
	char *fmt;
	{
		struct _iobuf _strbuf;

		strbuf._flag = _IOWRT | _IOSTRG;
		strbuf._cnt = len - 1;
		strbuf._ptr = buf;
		_doprnt(fmt, &arg, _strbuf);
		buf[len - 1] = '\0';
		return buf;
	}

   and call sprintfl with a `len' of (say) 50 and a fmt+arglist
   that comes out to more than 50 characters, guess what happens?
   _flsbuf writes the first 49 characters [len-1, remember?] to
   whatever file descriptor happens to be in _strbuf._file, or
   other similarly nasty things (the exact behaviour depends on
   what is in _strbuf._base).

   This means that if you pass a sufficient amount of stuff to
   sprintf, it will break, since it sets strbuf._flag as above
   (but sets strbuf._len to 32767).

   The (temporary) way around this is to leave out _IOWRT, which
   makes _flsbuf return an error, which makes _doprnt quit, which
   is essentially what is desired.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci (301) 454-7690
UUCP:	{seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland